This invention relates generally to solar collector apparatus, and more specifically to solar collector apparatus with a shaped collector surface that increases absorption and heat transfer efficiency for use with low cost materials, such as ceramics.
Solar energy is generally recognized as a potential source of power; however, the collection of the radiant energy from the sun and transforming it for use remains economically marginal. Materials having suitably high absorption and low emissivity characteristics are too expensive for general use. Therefore, the quest has continued for less expensive materials that have acceptable absorption and emissivity characteristics or for specially designed physical features which enhance the absorption and emissivity performance of less expensive materials. Numerous types of collector surfaces have been designed for the latter purpose, most of which have been directed to enhancing the radiation absorption characteristics and heat transfer efficiency of the systems. For example, the U.S. Pat. No. 3,985,116, invented by N. Kapany, the U.S. Pat. No. 3,232,795 invented by R. Gillette et al and the U.S. Pat. No. 4,007,728, invented by P. Guba, utilize truncated polyhedral formations on the panel surface to increase the number of radiation reflecting surfaces and direct them to a critical or common point. U.S. Pat. No. 4,030,477, invented by D. Smith, discloses a panel comprised of a plurality of conical configurations for focusing the radiation to a heat converter element, and U.S. Pat. No. 3,894,685, invented by J. Keyes et al, discloses an absorber panel with cylindrical cups on its surface. However, the economics of solar collector systems that utilize such designs still remains questionable either due to the use of relatively expensive, metallic, materials or high manufacturing costs. The success of such prior art inventions is even less impressive when an air heat transfer medium, rather than a liquid medium is used. In systems employing either type of heat transfer mechanism there is a continuing need for a solar collector panel which is capable of decreasing the emissivity and increasing the heat transfer characteristics of the absorber panel material in an efficient and more economical manner.